1. Field of the Invention
This invention relates to a device for rapidly heating up a fuel to its operating temperatures and more particularly, this invention relates to rapidly heating up a fuel processor so that it is able to deliver hydrogen (H2) to a fuel cell stack within as little as 30 seconds.
2. Background of the Invention
Fuel cells operate using hydrogen (H2) as an energy source to generate electrical power. Many of these fuel cell systems have duty cycles that require frequent starts and stops.
The earliest introduced fuel-cell-powered vehicles will find wide consumer acceptance if they can operate on widely available conventional fuels. As such, these revolutionary vehicles will need to include mini-refineries (known as fuel processors) to convert fuels such as gasoline, methanol, and other fuels to a hydrogen-rich reformate gas. Besides meeting stringent fuel cell operating parameters on the amount of carbon monoxide and sulfur that can be present in the reformate, these fuel processors should be energy-efficient, lightweight and compact enough to fit under the hood of a vehicle without compromising performance. Commercial success of these fuel cell systems will be contingent upon their ability to start-up within a very short time.
Typical fuel processors include several unit operations and processes, most of which are conducted at elevated (greater than 60° C.) temperatures. These processors define catalytic zones and heat exchangers that represent significant thermal mass. Raising these masses to their respective operating temperatures requires transferring thermal energy rapidly, but at a controlled rate so as to prevent damage of the material being heated.
Raising the temperature of a given mass in the processor requires heat. By reducing the thermal mass of the fuel processor (i. e., by not bringing all units of the processor to normal operational temperature during startup), the amount of fuel and time needed to generate this heat is reduced. The amount of fuel a processor requires to reach its operating temperature is the “fuel penalty.” “Fuel penalties” can become a significant portion of the total fuel used in power systems having short cycles. The more cycles in a particular amount of time, the more fuel used in that amount of time for start-up as a result of the “fuel penalty.” If the second cycle or trip occurs before the system cools down, the penalty is lower.
In many applications such as transportation, it is important to maintain a very short startup-time. Since today's automobiles are powered by internal combustion engines, today's drivers are accustomed to start-and-drive performance. If fuel cell power is to replace internal combustion power, start-up performance will be critical for commercial success It is anticipated that fuel cell vehicles will be hybridized with battery power that can provide propulsion power to the vehicle at startup while the fuel cell system warms up to become operational. The weight of batteries, and its resulting penalty on the car's fuel economy, means that the need for battery power should be limited to a very short duration. This implies that the battery should provide only minimal start-up support, and that the fuel processor itself must have fast-start capability.
A mass can be heated to its operating temperature by burning fuel. A given thermal mass, mCpΔT, (wherein m=mass, Cp=heat capacity, ΔT=temperature rise) can be heated to its operating temperature faster by increasing the rate of fuel combustion. However, the maximum rate at which this can be sustained depends on many factors such as the capacity of the fuel pump, the air blower/capacity, temperature control to prevent local overheating, and pressure drops through the components and flow passages.
U.S. Pat. No. 6,210,821 awarded to Lesieur, et al. on Apr. 3, 2001 discloses a method and apparatus for a fuel gas processing system. A rapid start-up method is not provided and the start-up is not run or initiated using conventional hydrocarbon-based fuels.
A need exists in the art for a quick start-up time for fuel processors for fuel cell power systems and a method by which a fuel processor can be started so it attains its operating temperature within a very short time. The method should require only a small equipment footprint so as to fit under the hood of a vehicle. The method should draw minimal amounts of electrical power and fuel. Finally, the method should be relatively inexpensive.